Ringworld and its related series is SF, set in Earth's future and a Dyson Ring (vs sphere... blow up a planet and put the bits in orbit around a star at about 1AU... build tall walls along the side to keep the atmosphere in.. live on the inner face with zillions of square miles of surface... serious proposal from Dyson, a serious guy). It's not only a great read, but a bona fide classic of SciFi.

If you don't want spoilers, quit reading here and go acquire a copy.

Or scroll down to continue.

What makes it particularly apropos The Knowledge community is that the civilization that built it collapsed. This is from the Wikipedia entry (CAUTION: Spoiler Alert!!!):

The downfall of the Ringworld's civilization: A mold that breaks down superconductors was introduced by a visiting spaceship. Without its superconductive technology, civilization fell.

In Ringworld, we get a look at how things might look to the people in the midst of Dark Age.

Less applicable, but stimulating, is the plight of the protagonists, who possess advanced but damaged technology and must search for assistance. Should The Knowledge be preserved, or even furthered, by a group isolated from other survivors of calamity, they may face analogous challenges.

Note that this collapse trigger is conceptually similar to that in The Lucifer Bug by our fellow forumite, Maurice Goldsmith. It would make an interesting companion read. Both are available in Kindle Edition, Ringworld is available in many editions and through many vendors.